Acoustic Microfluidic Separation Techniques and Bioapplications: A Review

Abstract

Microfluidic separation technology has garnered significant attention over the past decade where particles are being separated at a micro/nanoscale in a rapid, low-cost, and simple manner. Amongst a myriad of separation technologies that have emerged thus far, acoustic microfluidic separation techniques are extremely apt to applications involving biological samples attributed to various advantages, including high controllability, biocompatibility, and non-invasive, label-free features. With that being said, downsides such as low throughput and dependence on external equipment still impede successful commercialization from laboratory-based prototypes. Here, we present a comprehensive review of recent advances in acoustic microfluidic separation techniques, along with exemplary applications. Specifically, an inclusive overview of fundamental theory and background is presented, then two sets of mechanisms underlying acoustic separation, bulk acoustic wave and surface acoustic wave, are introduced and discussed. Upon these summaries, we present a variety of applications based on acoustic separation. The primary focus is given to those associated with biological samples such as blood cells, cancer cells, proteins, bacteria, viruses, and DNA/RNA. Finally, we highlight the benefits and challenges behind burgeoning developments in the field and discuss the future perspectives and an outlook towards robust, integrated, and commercialized devices based on acoustic microfluidic separation.

Preparation of Tissues and Heterogeneous Cellular Samples for Single-Cell Analysis

“…SAWs are further subdivided into standing SAWs (SSAWs) and traveling SAWs (TSAWs). The key difference between bulk waves and standing waves are that bulk waves, generated by a piezoelectric transducer, propagate through the bulk of the microchannel chamber itself, while surface acoustic waves, generated by an interdigitated transducer, Preparation of Tissues and Heterogeneous Cellular Samples for Single-Cell Analysis DOI: http://dx.doi.org/10.5772/intechopen.100184 propagate through the bottom surface of the channel [113]. Acoustofluidic systems are frequently used to sort cells via deformability or other elastic properties.…”

“…They can be separated by size due to differences in forces that dominate at different particle sizes. Specifically, acoustic radiation dominates in larger particles while drag forces induced by acoustic streaming dominate in smaller ones [113].…”

Acoustofluidic Medium Exchange for Preparation of Electrocompetent Bacteria Using Channel Wall Trapping

“…The most commonly used forces are dielectric, 12,[25][26][27][28] magnetic, 6,9,13,22,23 hydrodynamic, 18,29,30 and acoustic. 16,19,27,[31][32][33][34] However, each of these methods exhibits fundamental limitations, such as the requirement of low flow rates or particle labelling. In this work, medium exchange is achieved by first trapping bacterial cells by acoustic forces and subsequently flushing the channel with a new medium such as ultrapure water.…”

Focalization Performance Study of a Novel Bulk Acoustic Wave Device

“…The development of miniaturized laboratory instrumentations and procedures in portable, integrated automated systems in enhanced microfluidic platforms is mandatory to allow a widespread application of liquid biopsy in everyday use either in diagnostic or clinical practice [11][12][13][14]. Acoustophoretic devices among others [15][16][17][18][19][20] emerged in biomedical research, as well as in clinical and diagnostic fields [21,22], for the separation or trapping of particles and cells, the control of their trajectories or their encapsulation in droplets [23][24][25]. By this approach, particles subjected to an ultrasonic field, generated via bulk acoustic waves (BAW) or surface acoustic waves (SAW), are scattered or impinged by field waves, allowing the creation of an acoustic radiation force able to move particles towards the surrounding medium.…”